From: Haoze Xie The bridge netfilter fake rtable is embedded in struct net_bridge and is attached to bridged packets with skb_dst_set_noref(). If such a packet is queued to NFQUEUE, __nf_queue() upgrades that fake dst with skb_dst_force(). At that point the queued skb can hold a real dst reference after bridge teardown has started. The problem is not that every bridged packet needs its own dst reference. The problem is that NFQUEUE can keep the bridge private fake dst alive after unregister begins. Fix this by keeping the bridge fake dst model unchanged and pinning the bridge master device only while the packet sits in NFQUEUE. Record the bridge device in nf_queue_entry when the queued skb carries a bridge fake dst, take a device reference for the queue lifetime, and drop it when the queue entry is freed. This keeps netdev_priv(br->dev) alive until verdict completion, so the embedded fake rtable and its metrics backing storage cannot be freed out from under dst_release(). It also avoids the constant refcount bump and avoids using ipv4-specific dst helpers for IPv6 bridge traffic. Fixes: 34666d467cbf ("netfilter: bridge: move br_netfilter out of the core") Cc: stable@kernel.org Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Signed-off-by: Haoze Xie Signed-off-by: Ren Wei --- Changes in v3: - drop the per-packet fake dst refcounting from v2 - stop using ipv4-specific dst helpers for the fake dst - keep the existing bridge fake rtable model unchanged on the fast path - pin the bridge master device only when NFQUEUE upgrades a fake dst into an asynchronous queued reference - v2 Link: https://lore.kernel.org/all/831936f111e6e1f435f4f6247d07fe6a6624d271.1779680014.git.royenheart@gmail.com/ changes in v2: - spell out how NFQUEUE upgrades the fake dst into a real reference - switch to rt_dst_alloc() instead of br_netfilter-private dst_ops state - detach the bridge device with dst_dev_put() during teardown - keep the ref-holding contract local to bridge_parent_rtable() - v1 Link: https://lore.kernel.org/all/783d76ac83917b7302c1ec647794bd773bb1875a.1778687139.git.royenheart@gmail.com/ include/net/netfilter/nf_queue.h | 1 + net/netfilter/nf_queue.c | 27 +++++++++++++++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/include/net/netfilter/nf_queue.h b/include/net/netfilter/nf_queue.h index 3978c3174cdb..fc3e81c07364 100644 --- a/include/net/netfilter/nf_queue.h +++ b/include/net/netfilter/nf_queue.h @@ -18,6 +18,7 @@ struct nf_queue_entry { unsigned int id; unsigned int hook_index; /* index in hook_entries->hook[] */ #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) + struct net_device *bridge_dev; struct net_device *physin; struct net_device *physout; #endif diff --git a/net/netfilter/nf_queue.c b/net/netfilter/nf_queue.c index 57b450024a99..ba9e2f3fbd94 100644 --- a/net/netfilter/nf_queue.c +++ b/net/netfilter/nf_queue.c @@ -24,6 +24,27 @@ static const struct nf_queue_handler __rcu *nf_queue_handler; +#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) +static struct net_device *nf_queue_bridge_dev(const struct sk_buff *skb, + const struct nf_hook_state *state) +{ + struct dst_entry *dst = skb_dst(skb); + struct net_device *dev; + + if (state->pf != NFPROTO_BRIDGE || !nf_bridge_info_exists(skb)) + return NULL; + + if (!dst || !(dst->flags & DST_FAKE_RTABLE)) + return NULL; + + dev = READ_ONCE(dst->dev); + if (!dev || dev == blackhole_netdev) + return NULL; + + return dev; +} +#endif + /* * Hook for nfnetlink_queue to register its queue handler. * We do this so that most of the NFQUEUE code can be modular. @@ -68,6 +89,8 @@ static void nf_queue_entry_release_refs(struct nf_queue_entry *entry) nf_queue_sock_put(state->sk); #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) + if (entry->bridge_dev) + dev_put(entry->bridge_dev); dev_put(entry->physin); dev_put(entry->physout); #endif @@ -85,6 +108,7 @@ static void __nf_queue_entry_init_physdevs(struct nf_queue_entry *entry) #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) const struct sk_buff *skb = entry->skb; + entry->bridge_dev = NULL; if (nf_bridge_info_exists(skb)) { entry->physin = nf_bridge_get_physindev(skb, entry->state.net); entry->physout = nf_bridge_get_physoutdev(skb); @@ -108,6 +132,9 @@ bool nf_queue_entry_get_refs(struct nf_queue_entry *entry) dev_hold(state->out); #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) + entry->bridge_dev = nf_queue_bridge_dev(entry->skb, state); + if (entry->bridge_dev) + dev_hold(entry->bridge_dev); dev_hold(entry->physin); dev_hold(entry->physout); #endif -- 2.47.3